'\" t
.TH "SD_BUS_MESSAGE_GET_TYPE" "3" "" "systemd 257.1" "sd_bus_message_get_type"
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.SH "NAME"
sd_bus_message_get_type, sd_bus_message_get_error, sd_bus_message_get_errno, sd_bus_message_get_creds, sd_bus_message_is_signal, sd_bus_message_is_method_call, sd_bus_message_is_method_error \- Query bus message addressing/credentials metadata
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'int\ sd_bus_message_get_type('u
.BI "int sd_bus_message_get_type(sd_bus_message\ *" "m" ", uint8_t\ *" "type" ");"
.HP \w'sd_bus_error*\ sd_bus_message_get_error('u
.BI "sd_bus_error* sd_bus_message_get_error(sd_bus_message\ *" "m" ");"
.HP \w'int\ sd_bus_message_get_errno('u
.BI "int sd_bus_message_get_errno(sd_bus_message\ *" "m" ");"
.HP \w'sd_bus_creds*\ sd_bus_message_get_creds('u
.BI "sd_bus_creds* sd_bus_message_get_creds(sd_bus_message\ *" "m" ");"
.HP \w'int\ sd_bus_message_is_signal('u
.BI "int sd_bus_message_is_signal(sd_bus_message\ *" "m" ", const\ char\ *" "interface" ", const\ char\ *" "member" ");"
.HP \w'int\ sd_bus_message_is_method_call('u
.BI "int sd_bus_message_is_method_call(sd_bus_message\ *" "m" ", const\ char\ *" "interface" ", const\ char\ *" "member" ");"
.HP \w'int\ sd_bus_message_is_method_error('u
.BI "int sd_bus_message_is_method_error(sd_bus_message\ *" "m" ", const\ char\ *" "name" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_message_get_type()\fR
returns the type of a message in the output parameter
\fItype\fR, one of
\fBSD_BUS_MESSAGE_METHOD_CALL\fR,
\fBSD_BUS_MESSAGE_METHOD_RETURN\fR,
\fBSD_BUS_MESSAGE_METHOD_ERROR\fR,
\fBSD_BUS_MESSAGE_SIGNAL\fR\&. This type is either specified as a parameter when the message is created using
\fBsd_bus_message_new\fR(3), or is set automatically when the message is created using
\fBsd_bus_message_new_signal\fR(3),
\fBsd_bus_message_new_method_call\fR(3),
\fBsd_bus_message_new_method_error\fR(3)
and similar functions\&.
.PP
\fBsd_bus_message_get_error()\fR
returns the error stored in the message
\fIm\fR, if there is any\&. Otherwise, it returns
\fBNULL\fR\&.
\fBsd_bus_message_get_errno()\fR
returns the error stored in the message
\fIm\fR
as a positive errno\-style value, if there is any\&. Otherwise, it returns zero\&. Errors are mapped to errno values according to the default and any additional registered error mappings\&. See
\fBsd-bus-errors\fR(3)
and
\fBsd_bus_error_add_map\fR(3)\&.
.PP
\fBsd_bus_message_get_creds()\fR
returns the message credentials attached to the message
\fIm\fR\&. If no credentials are attached to the message, it returns
\fBNULL\fR\&. Ownership of the credentials instance is not transferred to the caller and hence should not be freed\&.
.PP
\fBsd_bus_message_is_signal()\fR
checks if message
\fIm\fR
is a signal message\&. If
\fIinterface\fR
is non\-null, it also checks if the message has the same interface set\&. If
\fImember\fR
is non\-null, it also checks if the message has the same member set\&. Also see
\fBsd_bus_message_new_signal\fR(3)\&. It returns true when all checks pass\&.
.PP
\fBsd_bus_message_is_method_call()\fR
checks if message
\fIm\fR
is a method call message\&. If
\fIinterface\fR
is non\-null, it also checks if the message has the same interface set\&. If
\fImember\fR
is non\-null, it also checks if the message has the same member set\&. Also see
\fBsd_bus_message_new_method_call\fR(3)\&. It returns true when all checks pass\&.
.PP
\fBsd_bus_message_is_method_error()\fR
checks if message
\fIm\fR
is an error reply message\&. If
\fIname\fR
is non\-null, it also checks if the message has the same error identifier set\&. Also see
\fBsd_bus_message_new_method_error\fR(3)\&. It returns true when all checks pass\&.
.SH "RETURN VALUE"
.PP
On success, these functions (except
\fBsd_bus_message_get_error()\fR
and
\fBsd_bus_message_get_creds()\fR) return a non\-negative integer\&. On failure, they return a negative errno\-style error code\&.
\fBsd_bus_message_get_errno()\fR
always returns a non\-negative integer, even on failure\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EINVAL\fR
.RS 4
The message parameter
\fIm\fR
or an output parameter is
\fBNULL\fR\&.
.RE
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_message_get_type()\fR,
\fBsd_bus_message_is_signal()\fR,
\fBsd_bus_message_is_method_call()\fR, and
\fBsd_bus_message_is_method_error()\fR
were added in version 240\&.
.PP
\fBsd_bus_message_get_error()\fR,
\fBsd_bus_message_get_errno()\fR, and
\fBsd_bus_message_get_creds()\fR
were added in version 246\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-bus\fR(3), \fBsd_bus_message_new\fR(3), \fBsd_bus_message_set_destination\fR(3), \fBsd-bus-errors\fR(3), \fBsd_bus_error_add_map\fR(3)
